High frequency induction heating coil



Jan. l5, 1935. J. HlRMANN l Y HIGH FREQUENCY INDUCTION HEATINGCOIL Filed man 1, 1934 FIG. 2

ATTORNEY N m R mm MH ms l wf ma,

Patented Jan. 15, 1935 UNITED STATES PATENT OFFICE 1,938,334 HIGH FBEQUENCYCIENUDUCTION HEATING Julius llirmann, Hillside, N. J., assignor to Radio Corporation ol America, a corporation of Del- Application ma 1, mi, semi No. 113,435 4 claim. (c1. :1s-'47) 5 ments of an electron discharge device during its manufacture.

In the manufacture of electron discharge dei vices the occluded gasesare removed from the metal elements or electrodes within the sealed envelope by heating. the electrodes. This heating is usually done by subjecting the electrodes of the electron discharge device to a high frequency electromagnetic field which by induction heats them to a relatively high temperature, thereby driving out the gases.

The high frequency coil generally used` to heat the electrodes of an electron discharge device, such as a. radio tube, is of the solenoid type, the tube being placed inside and'concentric with the turns of the coil. Some electrodes, such as certain types of anodes which are flat or boxlike, are difficult to heat, and require a large power input to the high frequency coil to bring about proper heating ofthe electrodes.

An object of my invention is to provide an improved type of induction heating coil which is simple, hightly elllcient and particularly adapted for heat treating flat or box type'electrodes of an electron discharge device.V

The novel features which I believe to be characteristic of my invention are set forth with particularly in the appended claims, but the invention itself will best be understood by reference to the following description taken in con' nection with the accompanying drawing in which:

Figure 1 shows a top view of a high frequency induction heating coil embodying my invention, with an electron discharge device in the coil in position to be heated.

Figure 2 shows a side view of the high frequency induction heating coil turned through 45 degrees and the electron discharge device shown in Figure l, and A Figure 3 is a reduced vertical cross section of an induction heating coil embodying my invention with an electron discharge device in position to be heated, the high frequency field produced by the coil being diagrammatically indicated.

The preferred embodiment of a high frequency heating coil made in accordance with my invention and shown in the drawing comprises a plurality of turns 10, preferably of copper tubing the turns being electrically connected in series. The turns have an elongated vertical transverse axis and are divided into two groups, each group comprising half the turns of the coil. The lower ends of each group are flared outwardly so as to provide oppositely disposed portions 11 and 12 lying in a plane substantially perpendicular to the plane of the longer vertical Vportion of the turns of the coil.

shown) by means of coupling members 16 and While I do notwish to be restricted to any particular theory, I explain the eectiveness of a high frequency coil embodying my invention as follows:

The heating eiect of a high frequency coil upon a metal electrode in its field depends upon the amount of flux or the lines lof force comprising the field of the coil which threads the electrode. With the usual helical or solenoid coil the field of the coil and the longitudinal axis of the electrodes to be heated are substantially parallel, hence only a very small part of the field actually threads at or box-like electrodes', and very little heating is obtained. Referring to Figure 3, it will be observed that the flux or lines of force comprising the field of the coil and represented by the lines having arrowheads, are substantially perpendicular to the plane of the fiat or box-like electrodes of the electron discharge device positioned within the coil and that the iield is most intense and uniform where it passes through the electrodes. Hence by the use of a coil embodying my invehtion the maximum amount of iiux threads the electrodes to be heated for a given expenditure'of energy and hence maximum heating is obtained under these conditions.

It will thus be seen that I have provided a simple and effective high frequency heating coil particularly adapted for heat treating the electrodes of the electron discharge device of the type described during manufacture of the device.

While I'have indicated the preferred embodiment of my invention of which I am now aware and have also indicated only one specific application for which my invention may be employed, it will be apparent that my invention is by no means limited to the exact forms illustrated or the use indicated, but that many variations may be made in the particular structure used and the purpose for which it is employed without departing from the scope of my invention as set forth in the appended claims.

What I claim as new is,

1. An induction heating coil comprising a plurality of turns electrically connected in series and lying in parallel planes, each coil having a corresponding portion flared outwardly to lie in a plane at an angle to said parallel planes whereby a pocket is formed within the turns of the coil for receiving an object extended perpendicularly to the longitudinal axis of said coil. A

2. An induction heating coil comprising a plurality of turns electrically connected in series and lying in parallel planes, each coil having a portion flared outwardly to lie in a plane substantially perpendicular to said parallel planes whereby a pocket is formed within the turns of the coil for receiving an object extended perpendicularly to the longitudinal axis of said coil.

3. An induction heating coil comprising a plurality of turns electrically connected in series and having an elongated transverse axis, the turns being formed to have one end flared outwardly from the plane of the main portion of the turns to lie in a plane substantially perpendicular to the plane of the main portion of the turns whereby a pocket is formed within the coil.

4. induction heating coil comprising a plurality of turns electrically connected in series and having an elongated transverse axis, s'ome of said turns having a portion at one end flared outwardly in one direction and the other turns having a portion at the same end flared outwardly in the opposite direction so that said flared portions are' oppositely disposed and provide an opening to receive within said coil an object extended perpendicularly to the longitudinal axis of said coil.

JULIUS HIRMANN. 

